1. Field of the Invention
The present invention pertains to a transition between two longitudinal sections of belt conveyors where a series of objects conveyed on the ending section of one conveyor are transferred by a pair of guide rails laterally over to a beginning section of the second conveyor. In particular, the present invention pertains to a source of vacuum positioned between the ending section of the one conveyor and the beginning section of the second conveyor where the source of vacuum holds the conveyed objects to the two conveyor surfaces as the objects are transferred between the two surfaces and thereby eliminates the problem of one or more conveyed objects falling over as they are transferred from the one conveyor surface to the second conveyor surface.
2. Description of the Related Art
Belt conveyors are often used in manufacturing and packaging facilities to quickly transfer a series of objects being manufactured and/or packaged from one area of the facility to another. A typical type of belt conveyor is a table top, chain conveyor that is comprised of a plurality of panels that are connected together, end to end, in a chain linked manner forming a continuous loop or belt from the plurality of panels. The belt of panels is supported and driven by a drive sprocket/pulley at one end and an idler or driven sprocket/pulley at its opposite end. The upper plurality of panels extending between the two pulleys defines a support surface of the conveyor that functions as a conveying surface that conveys objects supported on the conveying surface from one end of the conveyor to the opposite end. The intermediate portion of the belt between the two pulleys is typically supported by laterally spaced sliding surfaces positioned beneath the portion of the belt. The belt rests on the sliding surfaces and slides across the surfaces between the pulleys at the opposite ends of the belts.
By supporting the length of the conveyor belt between the drive and driven pulleys with the sliding surface positioned beneath the upper section of the belt, the conveyor belt can extend for a considerable length between the drive and driven pulleys. However, the longer the conveyor belt, the more power is required of the motor driving the conveyor belt drive pulley. Therefore, it is often necessary to employ two or more conveyor belt assemblies to convey objects for longer distances.
To provide a continuous conveyor path between two or more belt conveyors, a beginning section of a second or downstream conveyor belt assembly is positioned adjacent and to one side of an ending section of a first or upstream conveyor belt assembly. With the beginning portion of the downstream belt assembly positioned adjacent the ending portion of the upstream belt assembly, the two conveyor belt assemblies provide a continuous conveyor path for objects conveyed on the supporting surfaces of the two belt assemblies. Pairs of guide rails are positioned over the conveying surfaces of the two belt assemblies and are connected by pairs of curved or S-shaped guide rails. The S-shaped guide rails connect the pair of parallel guide rails that extend over the length of the upstream conveyor belt with the pair of parallel guide rails that extend over the length of the downstream conveyor belt. The pair of S-shaped guide rails gradually curve from positions over the upstream conveyor support surface, across the transition area between the two overlapping sections of the conveyors, to positions over the downstream conveyor support surface. The S-shaped guide rails gradually channel the stream of objects conveyed by the upstream conveyor support surface over the transition area between the two conveyors to the downstream conveyor support surface.
To convey a stream of lightweight objects, for example empty, plastic blow molded bottles, vacuum pressure is often used to hold the lightweight objects down on the conveying surface of a conveyor. Holes are provided through the plates of the conveyor to communicate a source of vacuum pressure beneath the conveyor with the conveying surface of the conveyor and to hold lightweight objects down on the conveying surface as they are conveyed along the length of the conveyor. However, due to the constructions of the belt conveyors and the manner in which the interlinked belt plates are supported from their undersides along the laterally opposite edges of the plates, the holes in the plates of the belt could only be positioned along the centers of the lengths of the conveyors. This proved to be a problem when a stream of objects is transitioned from the ending portion of one conveyor to the beginning portion of an adjacent conveyor. As the S-shaped transition guide rails would push the stream of objects from the ending portion of one conveyor across the conveyor transition area to the beginning portion of the second conveyor, the guide rails would push the stream of objects away from the source of vacuum pressure of the one conveyor, across the transition, toward the source of vacuum pressure of the second conveyor. Thus, as the bottles would be transitioned from the ending portion of one conveyor to the beginning portion of the second conveyor, there would be no vacuum pressure available to hold the stream of objects down on the two conveying surfaces. Furthermore, as the stream of objects is channeled through the S-shaped transition, the engagement of the lightweight objects with the S-shaped guide rails that push the objects laterally across from one conveyor to the other conveyor would often impart a spin to the bottles. The spin produced by the conveyor guide rails and the absence of vacuum pressure holding the lightweight objects on the conveying surfaces would often result in one or more of the lightweight objects being toppled over on the conveying surfaces disrupting the continuous stream of upright conveyed objects.
To address this problem, a plurality of holes of the same size and shape were provided in the gap between the ending portion of the one conveyor and the beginning portion of the other conveyor. These holes communicated with the vacuum source and provided vacuum pressure in the gap between the ending portion of the one conveyor and the beginning portion of the other conveyor and were effective in holding the lightweight conveyed objects to the conveying surfaces of the two conveyor portions. However, this remedy was found to be insufficient to eliminate the problem of the guide rails S-shaped transition portions imparting a spin to the lightweight conveyed objects that would cause the objects to topple over as they are conveyed through the transition.
What is needed is a means of eliminating the problem of lightweight objects conveyed through the S-shaped guide rail transition between the ending portion of one conveyor and the beginning portion of another conveyor from toppling over in the transition section.
The present invention addresses the problem of lightweight conveyed objects, for example empty plastic blow molded bottles, toppling over in the S-shaped guide rails transition between the ending portion of an upstream conveyor and the beginning portion of a downstream conveyor by providing an improved distribution of vacuum pressure in the gap between the two conveyor portions.
The belt conveyor transition of the present invention is constructed along a typical transition between an ending portion of an upstream belt conveyor and a beginning portion of a downstream belt conveyor. The ending portion of the upstream conveyor and the beginning portion of the downstream conveyor overlap in a side-by-side relationship. The conveying surface of the ending portion of the upstream conveyor is positioned in the same plane and adjacent the conveying surface of the beginning portion of the downstream belt conveyor. There is a small lateral gap between the ending portion and the beginning portion of the two conveyors.
A source of vacuum pressure is provided in the gap between the two conveyor portions. However, unlike the prior art source of vacuum pressure provided by a plurality of identical holes communicating with the vacuum sources, the vacuum stabilization of the present invention is provided by a varying degree of vacuum pressure in the lateral gap between the two conveyor portions. As the S-shaped conveyor guide rails extend across the transition area from the ending portion of the upstream conveyor to the beginning portion of the downstream conveyor, the source of vacuum pressure provided by the vacuum stabilization system of the invention is at its greatest as the transition across the conveyor portions begins and then gradually decreases in the downstream direction. In this manner) the strongest vacuum pressure that holds the stream of objects conveyed from the conveying surface of one conveyor to the other is provided at the beginning of the transition period and then gradually decreases as the stream of objects is conveyed from the upstream conveyor to the downstream conveyor.
The variable source of vacuum pressure of the vacuum stabilization system of the invention is provided by a plurality of apertures arranged in the gap between the two conveyor portions where the apertures are of different sizes and/or shapes. The apertures communicate with a vacuum source provided through a plenum positioned below the two conveying surfaces. In the preferred embodiment of the invention, the apertures are provided in a single line that extends in the downstream direction between the two conveying surfaces. In addition, several of the apertures at the beginning of the line of apertures have larger areas than several of the apertures at the end or downstream end of the line of apertures. Still further, several of the apertures at the beginning of the line are given oblong configurations with their major axes being larger than their minor axes and with their major axes extending in the downstream direction. These oblong apertures are arranged end to end along the line of apertures. However, the oblong apertures are only positioned at the beginning of the transition section and several circular apertures are arranged at the end of the transition section. Together, the several oblong apertures and circular apertures make up the plurality of apertures of the vacuum stabilization system. By providing larger, oblong-shaped apertures at the beginning of the transition section and smaller, circular apertures at the end of the transition section, the vacuum stabilization system of the invention provides a stronger vacuum source at the beginning of the transition of the conveyed objects from the upstream conveyor section to the downstream conveyor section. When the transition of the conveyor objects from the upstream section to the downstream section is substantially completed, the plurality of apertures change over to the smaller, circular apertures where a greater vacuum force is not needed to stabilize the lightweight objects as they are conveyed through the transition section.
By providing the plurality of apertures in a single line through the gap between the two conveyor surfaces and providing the apertures with larger shaped and sized apertures at the beginning or upstream end of the line than the apertures at the end or downstream end of the line, the vacuum stabilization system of the invention provides a greater source of vacuum pressure at the beginning of the conveyor transition where the stream of conveyed objects are first pushed away from the vacuum source of the upstream conveyor belt. The vacuum stabilization system also provides a gradually decreasing source of vacuum pressure in the gap between the two belt sections as the stream of objects are pushed by the S-shaped guide rails across the gap and onto the source of vacuum pressure of the downstream conveyor section.